Re: [PATCH 0/4] Swap migration V3: Overview

[KAMEZAWA Hiroyuki]

mike kravetz wrote:
> > > Just to be clear, there are at least two distinct requirements for hotplug.
> > > One only wants to remove a quantity of memory (location unimportant).  The
> > > other wants to remove a specific section of memory (location specific).  I
> > > think the first is easier to address.
> >
> > The only difficulty to remove a quantity of memory is how to find
> > where is easy to be removed. If this is fixed, I think it is
> > easier to address.
>
>
> We have been using Mel's fragmentation patches.  One of the data structures
> created by these patches is a 'usemap' thats tracks how 'blocks' of memory
> are used.  I exposed the usemaps via sysfs along with other hotplug memory
> section attributes.  So, you can then have a user space program scan the
> usemaps looking for sections that can be easily offlined.
yea, looks nice :)
But such pages are already shown as hotpluggable, I think.
ACPI/SRAT will define the range, in ia64.

The difficulty is how to find hard-to-migrate pages, as Andrew pointed out.



Thanks,
-- Kame

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